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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Synthesis, crystal and electronic structure of the Zintl phase Ba 16 Sb 11 . A case study uncovering greater structural complexity via monoclinic distortion of the tetragonal Ca 16 Sb 11 structure type

The binary Zintl phase Ba 16 Sb 11 has been synthesized and structurally characterized. Detailed studies via single-crystal X-ray diffraction methods indicate that although Ba 16 Sb 11 appears to crystallize in the tetragonal Ca 16 Sb 11 structure type (space group $P\bar{4}2_1$m with a=13.5647(9) Å, c=12.4124(12)Å, Z=2, R 1 = 3.14%; wR 2 = 4.77%), there exists an extensive structural disorder. Some Ba 16 Sb 11 crystals were found to be monoclinic and the structure was solved and refined in space group P2 1 (a=18.3929(12) Å, b=13.5233(8) Å, c=18.3978(12) Å, β=94.6600(10)°; Z=4, R 1 =5.84 %; wR 2 =9.58 %). The latter corresponds to a 2-fold superstructure of the tetragonal one, which provides a disorder-free structural model. In both descriptions, the disordered tetragonal and the ordered monoclinic superstructure, the basic building units that make up the structure of this Ba-rich compound are pairs of face-shared square antiprisms of Ba atoms, which are centered by Sb atoms. The dimerized antiprisms are linked into parallel chains via square prisms of Ba atoms, which are also centered by Sb atoms. The Zintl concept can be applied in a straightforward manner and as result, the structure of Ba 32 Sb 22 (=2×Ba 16 Sb 11 ) can be rationalized as (Ba 2+ ) 32 (Sb 3– ) 20 [Sb 2 ] 4– . Notably, the partitioning of the valence electrons is done taking into an account the homoatomic Sb–Sb contacts (d=3.01 Å), which can be clearly distinguished in the lower symmetry space group. Electronic structure calculations of Ba 16 Sb 11 are in good accordance with the Zintl rationalization and predict a semiconductor with a band gap of 0.77 eV.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Ba(H2O3)2 by Materials Project

Ba(H2O3)2 crystallizes in the monoclinic Cc space group. The structure is three-dimensional. Ba is bonded in a 10-coordinate geometry to ten O atoms. There are a spread of Ba–O bond distances ranging from 2.80–2.99 Å. There are four inequivalent H sites. In the first H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.06 Å) and one longer (1.49 Å) H–O bond length. In the second H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.07 Å) and one longer (1.43 Å) H–O bond length. In the third H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.08 Å) and one longer (1.43 Å) H–O bond length. In the fourth H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.07 Å) and one longer (1.46 Å) H–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to two equivalent Ba and one H atom. In the second O site, O is bonded in a single-bond geometry to two equivalent Ba and one H atom. In the third O site, O is bonded in a single-bond geometry to two equivalent Ba and one H atom. In the fourth O site, O is bonded in a single-bond geometry to two equivalent Ba and one H atom. In the fifth O site, O is bonded in a distorted bent 150 degrees geometry to one Ba and two H atoms. In the sixth O site, O is bonded in a distorted bent 150 degrees geometry to one Ba and two H atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(HO2)2 by Materials Project

Ba(HO2)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ba is bonded in a 12-coordinate geometry to one H and eleven O atoms. The Ba–H bond length is 2.99 Å. There are a spread of Ba–O bond distances ranging from 2.78–3.33 Å. There are two inequivalent H sites. In the first H site, H is bonded in a linear geometry to one Ba and two O atoms. There is one shorter (1.14 Å) and one longer (1.32 Å) H–O bond length. In the second H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.07 Å) and one longer (1.46 Å) H–O bond length. There are four inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to three equivalent Ba and one H atom. In the second O site, O is bonded in a single-bond geometry to three equivalent Ba and one H atom. In the third O site, O is bonded in a distorted single-bond geometry to three equivalent Ba and one H atom. In the fourth O site, O is bonded in a single-bond geometry to two equivalent Ba and one H atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(H2O3)2 by Materials Project

Ba(H2O3)2 crystallizes in the monoclinic Cc space group. The structure is three-dimensional. Ba is bonded in a 12-coordinate geometry to twelve O atoms. There are a spread of Ba–O bond distances ranging from 2.81–3.03 Å. There are four inequivalent H sites. In the first H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.07 Å) and one longer (1.48 Å) H–O bond length. In the second H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.07 Å) and one longer (1.47 Å) H–O bond length. In the third H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.07 Å) and one longer (1.47 Å) H–O bond length. In the fourth H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.07 Å) and one longer (1.47 Å) H–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to two equivalent Ba and one H atom. In the second O site, O is bonded in a single-bond geometry to two equivalent Ba and one H atom. In the third O site, O is bonded in a single-bond geometry to two equivalent Ba and one H atom. In the fourth O site, O is bonded in a single-bond geometry to two equivalent Ba and one H atom. In the fifth O site, O is bonded in a distorted bent 150 degrees geometry to two equivalent Ba and two H atoms. In the sixth O site, O is bonded in a distorted bent 150 degrees geometry to two equivalent Ba and two H atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

An ab initio molecular dynamics exploration of associates in Ba-Bi liquid with strong ordering trends

Fictive associates are widely used to describe and model liquid phases with strong ordering trends. However, little evidence is known about the assumed associates in most cases. In the present work, an ab initio molecular dynamics (AIMD) study is employed to investigate the characters of the Ba-Bi liquid, in which associates have been assumed in existing thermodynamic modeling. It is found that in the Ba rich melt, the Bi atoms are almost completely surrounded by Ba atoms. The Bi-centered coordination polyhedrons are strongly associated to crystalline structures of Ba 5 Bi 3 and Ba 4 Bi 3 with a longer lifetime than other polyhedrons during the AIMD simulations. In addition, these Bi-centered polyhedrons in Ba rich melt connect with each other through vertex, edge, face, and/or bipyramid sharing to form medium range orders (MRO). In the Bi rich melt, the Ba-centered polyhedrons also form MROs, but they are both structurally and compositionally diverse with a shorter lifetime. These findings from AIMD study provide evidences that there exist a strongly ordering Ba 4 Bi 3 associate and a weakly ordering BaBi 3 associate in the Ba-Bi liquid. Here, the predicted enthalpy of mixing in the liquid agrees well with the results by the CALPHAD modeling in the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(MgPb)2 by Materials Project

Ba(MgPb)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Ba is bonded in a 12-coordinate geometry to eight Mg and eight Pb atoms. There are four shorter (3.82 Å) and four longer (4.03 Å) Ba–Mg bond lengths. There are four shorter (3.85 Å) and four longer (3.97 Å) Ba–Pb bond lengths. There are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 5-coordinate geometry to four equivalent Ba and five Pb atoms. There are one shorter (2.86 Å) and four longer (3.03 Å) Mg–Pb bond lengths. In the second Mg site, Mg is bonded to four equivalent Ba and four equivalent Pb atoms to form MgBa4Pb4 tetrahedra that share corners with twelve equivalent PbBa4Mg4 tetrahedra, edges with two equivalent PbBa4Mg4 tetrahedra, edges with four equivalent MgBa4Pb4 tetrahedra, and faces with four equivalent MgBa4Pb4 tetrahedra. All Mg–Pb bond lengths are 3.02 Å. There are two inequivalent Pb sites. In the first Pb site, Pb is bonded in a 9-coordinate geometry to four equivalent Ba and five Mg atoms. In the second Pb site, Pb is bonded to four equivalent Ba and four equivalent Mg atoms to form distorted PbBa4Mg4 tetrahedra that share corners with twelve equivalent MgBa4Pb4 tetrahedra, edges with two equivalent MgBa4Pb4 tetrahedra, edges with four equivalent PbBa4Mg4 tetrahedra, and faces with four equivalent PbBa4Mg4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(GaPt)2 by Materials Project

Ba(PtGa)2 is alpha Pu-derived structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ba is bonded in a 2-coordinate geometry to eight Pt and nine Ga atoms. There are a spread of Ba–Pt bond distances ranging from 3.32–4.01 Å. There are a spread of Ba–Ga bond distances ranging from 3.44–3.89 Å. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded in a 4-coordinate geometry to four equivalent Ba and four Ga atoms. There are a spread of Pt–Ga bond distances ranging from 2.47–2.56 Å. In the second Pt site, Pt is bonded in a 6-coordinate geometry to four equivalent Ba and four Ga atoms. There are a spread of Pt–Ga bond distances ranging from 2.49–2.59 Å. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a 4-coordinate geometry to four equivalent Ba and four Pt atoms. In the second Ga site, Ga is bonded in a 4-coordinate geometry to five equivalent Ba and four Pt atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(BiPd)2 by Materials Project

Ba(PdBi)2 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Ba is bonded in a 1-coordinate geometry to eight Pd and eight Bi atoms. There are a spread of Ba–Pd bond distances ranging from 3.40–3.92 Å. There are a spread of Ba–Bi bond distances ranging from 3.70–3.84 Å. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a 9-coordinate geometry to four equivalent Ba and five Bi atoms. There are a spread of Pd–Bi bond distances ranging from 2.82–2.88 Å. In the second Pd site, Pd is bonded in a 10-coordinate geometry to four equivalent Ba, two equivalent Pd, and four equivalent Bi atoms. Both Pd–Pd bond lengths are 3.15 Å. There are a spread of Pd–Bi bond distances ranging from 2.78–2.88 Å. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded in a 5-coordinate geometry to four equivalent Ba and five Pd atoms. In the second Bi site, Bi is bonded in a 4-coordinate geometry to four equivalent Ba and four equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(InAu)2 by Materials Project

Ba(AuIn)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba is bonded in a 1-coordinate geometry to seven Au and four In atoms. There are a spread of Ba–Au bond distances ranging from 3.32–3.67 Å. There are a spread of Ba–In bond distances ranging from 3.64–3.74 Å. There are two inequivalent Au sites. In the first Au site, Au is bonded in a 9-coordinate geometry to three equivalent Ba, two equivalent Au, and four In atoms. Both Au–Au bond lengths are 2.95 Å. There are a spread of Au–In bond distances ranging from 2.78–2.91 Å. In the second Au site, Au is bonded in a 9-coordinate geometry to four equivalent Ba and five In atoms. There are a spread of Au–In bond distances ranging from 2.87–2.99 Å. There are two inequivalent In sites. In the first In site, In is bonded in a 7-coordinate geometry to two equivalent Ba and five Au atoms. In the second In site, In is bonded to two equivalent Ba and four Au atoms to form a mixture of distorted edge and corner-sharing InBa2Au4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(H8O5)2 by Materials Project

Ba(H8O5)2 crystallizes in the monoclinic C2/c space group. The structure is two-dimensional and consists of two Ba(H8O5)2 sheets oriented in the (0, 0, 1) direction. Ba is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ba–O bond distances ranging from 2.80–2.85 Å. There are eight inequivalent H sites. In the first H site, H is bonded in a distorted linear geometry to two O atoms. There is one shorter (1.02 Å) and one longer (1.61 Å) H–O bond length. In the second H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 1.00 Å. In the third H site, H is bonded in a distorted linear geometry to two O atoms. There is one shorter (1.02 Å) and one longer (1.64 Å) H–O bond length. In the fourth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 1.00 Å. In the fifth H site, H is bonded in a distorted linear geometry to two O atoms. There is one shorter (1.02 Å) and one longer (1.63 Å) H–O bond length. In the sixth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 1.00 Å. In the seventh H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 1.00 Å. In the eighth H site, H is bonded in a distorted linear geometry to two O atoms. There is one shorter (1.02 Å) and one longer (1.63 Å) H–O bond length. There are five inequivalent O sites. In the first O site, O is bonded in a 5-coordinate geometry to four H and one O atom. The O–O bond length is 1.49 Å. In the second O site, O is bonded in a water-like geometry to one Ba and two H atoms. In the third O site, O is bonded in a water-like geometry to one Ba and two H atoms. In the fourth O site, O is bonded in a water-like geometry to one Ba and two H atoms. In the fifth O site, O is bonded in a water-like geometry to one Ba and two H atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(CO3)2 by Materials Project

Ba(C1O3)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ba is bonded in a 5-coordinate geometry to eight O atoms. There are a spread of Ba–O bond distances ranging from 2.69–3.43 Å. There are two inequivalent C sites. In the first C site, C is bonded in a distorted bent 120 degrees geometry to two O atoms. Both C–O bond lengths are 1.27 Å. In the second C site, C is bonded in a distorted bent 120 degrees geometry to two O atoms. There is one shorter (1.26 Å) and one longer (1.27 Å) C–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.24 Å. In the second O site, O is bonded in a distorted single-bond geometry to two equivalent Ba and one C atom. In the third O site, O is bonded in a distorted single-bond geometry to one Ba and one C atom. In the fourth O site, O is bonded in a distorted single-bond geometry to two equivalent Ba and one C atom. In the fifth O site, O is bonded in a distorted trigonal non-coplanar geometry to two equivalent Ba and one O atom. In the sixth O site, O is bonded in a distorted single-bond geometry to one Ba and one C atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(CoSn4)2 by Materials Project

Ba(CoSn4)2 crystallizes in the orthorhombic Cccm space group. The structure is three-dimensional. Ba is bonded in a 2-coordinate geometry to thirteen Sn atoms. There are a spread of Ba–Sn bond distances ranging from 3.54–4.01 Å. Co is bonded in a 7-coordinate geometry to seven Sn atoms. There are a spread of Co–Sn bond distances ranging from 2.56–2.70 Å. There are seven inequivalent Sn sites. In the first Sn site, Sn is bonded in a 2-coordinate geometry to two equivalent Ba and two equivalent Co atoms. In the second Sn site, Sn is bonded in a 10-coordinate geometry to two equivalent Ba, two equivalent Co, and one Sn atom. The Sn–Sn bond length is 3.19 Å. In the third Sn site, Sn is bonded in a 1-coordinate geometry to two equivalent Ba, one Co, and two Sn atoms. There are one shorter (3.16 Å) and one longer (3.21 Å) Sn–Sn bond lengths. In the fourth Sn site, Sn is bonded in a 12-coordinate geometry to four equivalent Co atoms. In the fifth Sn site, Sn is bonded in a 2-coordinate geometry to one Ba, two equivalent Co, and five Sn atoms. The Sn–Sn bond length is 2.99 Å. In the sixth Sn site, Sn is bonded in a distorted octahedral geometry to six Sn atoms. Both Sn–Sn bond lengths are 3.13 Å. In the seventh Sn site, Sn is bonded in a 5-coordinate geometry to two equivalent Ba, two equivalent Co, and one Sn atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ClO)2 by Materials Project

Ba(OCl)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ba is bonded in a 9-coordinate geometry to four O and five Cl atoms. There are a spread of Ba–O bond distances ranging from 2.73–2.79 Å. There are a spread of Ba–Cl bond distances ranging from 3.22–3.48 Å. There are two inequivalent O sites. In the first O site, O is bonded in a distorted bent 120 degrees geometry to two equivalent Ba and two equivalent Cl atoms. There are one shorter (2.41 Å) and one longer (2.45 Å) O–Cl bond lengths. In the second O site, O is bonded in a distorted bent 150 degrees geometry to two equivalent Ba and two Cl atoms. There are one shorter (2.41 Å) and one longer (2.48 Å) O–Cl bond lengths. There are two inequivalent Cl sites. In the first Cl site, Cl is bonded in a 1-coordinate geometry to four equivalent Ba and one O atom. In the second Cl site, Cl is bonded in a 4-coordinate geometry to one Ba and three O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(SbO2)3 by Materials Project

Ba(SbO2)3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ba is bonded in a 10-coordinate geometry to ten O atoms. There are a spread of Ba–O bond distances ranging from 2.71–3.24 Å. There are three inequivalent Sb sites. In the first Sb site, Sb is bonded in a 4-coordinate geometry to four O atoms. There are a spread of Sb–O bond distances ranging from 1.98–2.51 Å. In the second Sb site, Sb is bonded in a distorted see-saw-like geometry to four O atoms. There are a spread of Sb–O bond distances ranging from 1.95–2.15 Å. In the third Sb site, Sb is bonded in a distorted rectangular see-saw-like geometry to four O atoms. There are a spread of Sb–O bond distances ranging from 1.90–2.20 Å. There are six inequivalent O sites. In the first O site, O is bonded in a 4-coordinate geometry to two equivalent Ba and two Sb atoms. In the second O site, O is bonded in a 4-coordinate geometry to two equivalent Ba and two Sb atoms. In the third O site, O is bonded in a distorted T-shaped geometry to three Sb atoms. In the fourth O site, O is bonded in a 1-coordinate geometry to three equivalent Ba and one Sb atom. In the fifth O site, O is bonded in a 2-coordinate geometry to one Ba and two Sb atoms. In the sixth O site, O is bonded in a 4-coordinate geometry to two equivalent Ba and two Sb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(GaO3)2 by Materials Project

Ba(GaO3)2 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Ba is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Ba–O bond distances ranging from 2.71–2.96 Å. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded to four O atoms to form corner-sharing GaO4 tetrahedra. There are a spread of Ga–O bond distances ranging from 1.83–1.89 Å. In the second Ga site, Ga is bonded to four O atoms to form corner-sharing GaO4 tetrahedra. There is one shorter (1.86 Å) and three longer (1.87 Å) Ga–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a distorted trigonal planar geometry to one Ba and two Ga atoms. In the second O site, O is bonded in a distorted trigonal planar geometry to two equivalent Ba and one Ga atom. In the third O site, O is bonded in a 1-coordinate geometry to two equivalent Ba and one Ga atom. In the fourth O site, O is bonded in a distorted trigonal planar geometry to two equivalent Ba and one Ga atom. In the fifth O site, O is bonded in a bent 120 degrees geometry to two Ga atoms. In the sixth O site, O is bonded in a distorted single-bond geometry to two equivalent Ba and one Ga atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Utilization of Novel (KNbO 3 ) 1− x (Ba 2 FeNbO 6 ) x ( x = 0.1, 0.2, 0.3) Solid Solutions for Efficient Photo‐Assisted Fenton Degradation of Methylene Blue Dye

Novel (KNbO 3 ) 1− x (Ba 2 FeNbO 6 ) x ( x = 0.1, 0.2, 0.3) solid solutions corresponding to K 0.82 Ba 0.18 Fe 0.09 Nb 0.91 O 3 , K 0.64 Ba 0.36 Fe 0.18 Nb 0.82 O 3 , and K 0.46 Ba 0.54 Fe 0.27 Nb 0.73 O 3 compounds have been synthesized via molten salt method. X‐ray diffraction confirms the formation of solid solutions, while transmission electron microscopy combined with energy‐dispersive spectroscopy results demonstrates a homogeneous distribution of elements. The obtained solid solutions crystallized in a cubic crystal structure, whereas the parent KNbO 3 possesses an orthorhombic structure. The wide bandgap semiconductor KNbO 3 transformed into a visible‐light‐active material, with its bandgap energy reduced from 3.56 eV to ≈2.4 eV. The substitution of K in KNbO 3 with Ba is responsible for structural modification from orthorhombic to cubic symmetry, whereas both structural modification and the substitution of Nb with Fe correlated with optical properties. The photocatalytic activities of all obtained solid solutions are improved compared with the parent KNbO 3 and Ba 2 FeNbO 6 compounds for photocatalytic degradation of methylene blue (MB) dye. Among the series of solid solutions, K 0.82 Ba 0.18 Fe 0.09 Nb 0.91 O 3 photocatalysts show the highest MB removal efficiency owing to its relatively higher surface area, suppressed charge carrier recombination, and more negative conduction band edge. Moreover, K 0.82 Ba 0.18 Fe 0.09 Nb 0.91 O 3 photocatalyst (0.1 g) combined with hydrogen peroxide (H 2 O 2 ) to form a novel photo‐Fenton system, achieving almost complete degradation of 100 mL of 10 mg L −1 MB dye in 30 min.

Avcıoğlu, Celal [Technische Universität Berlin, Fa↗
DOE OSTI2025

New layered quaternary Zintl pnictide oxides Ba 2 Zn 2 Pn 2 O ( Pn = Sb, Bi): Discovery, crystal structures, band engineering, and transport properties

Three new heteroanionic oxypnictides, Ba 2 Zn 2 Sb 2 O, Ba 2 Zn 2 Bi 2 O, and the solid solution Ba 2 Zn 2 Sb 2−x Bi x O (x ≈ 1.1–1.6), have been synthesized and structurally characterized. They are isostructural with their Mn-bearing analog, adopting the Ba 2 Mn 2 Sb 2 O-type structure (space group P6 3 /mmc, No. 194), and feature a double-layered 2D $^{2}_{∞}$ [Zn 2 Pn 2 O] 2- substructure (Pn = Sb, Bi, Sb/Bi) composed of corner-sharing, distorted tetrahedral ZnPn 3 O units. Electronic structure calculations reveal a systematic progression from semiconducting Ba 2 Zn 2 Sb 2 O to metallic Ba 2 Zn 2 Bi 2 O as Bi content increases. These trends are corroborated by transport property measurements, with Ba 2 Zn 2 Sb 0.9(1) Bi 1.1 O exhibiting relatively low electrical resistivity, high Hall mobilities of ∼160 cm 2 /V·s, and large Seebeck coefficients from 69 to 132 μV K −1 over the 300–600 K temperature range. Comparison with structurally related Zintl pnictides, such as SrIn 2 As 2 and PrZn 3 As 3 phases, situates Ba 2 Zn 2 Pn 2 O (Pn = Sb, Bi) within a broader family of heteroanionic oxypnictide Zintl compounds, highlighting their structural flexibility and amenability to band engineering. Finally, electronic structure and bonding considerations point to tunable semiconducting behavior and underscore the relevance of these materials for thermoelectric and topological applications.

Band engineering↗
NASA NTRS1994

Geometry and Unoccupied Electronic States of Ba and BaO on W(001)

A study aimed at understanding the geometrical and electronic properties of barium and oxygen coadsorbed on the tungsten(001) surface has been carried out by means of work-function measurements (Delta-phi), Auger-electron spectroscopy, low-energy electron diffraction, inverse photoelectron spectroscopy, and relativistic-electronic-structure calculations. A report of the experimental measurements and a comparison with theoretical results from embedded-cluster-model calculations are presented. Our experimental studies show that the work function of the W(001) surface (phi = 4.63 eV) is lowered to approximately 2.3-2.4 eV by coadsorption of 1 ML of Ba and O regardless of the order of deposition of these two species. The technique of IPS in the isochromat mode was used to determine the unoccupied electronic-energy band structure for ordered c (2 X 2) Ba and O layers on W(001). Several spectral features are observed above the Fermi level (E(F)), which we assign to transitions into Ba and W d-states. The measured two-dimensional electronic band structure is independent of the order of Ba and O deposition. Using embedded-cluster-model calculations, we investigated two possible adsorption configurations of an ordered c(2 X 2) adlayer of Ba and O on W(001): 'tilted,' where Ba and O are placed on alternate fourfold-hollow sites, and 'upright,' where the adsorbed atoms lay above the same site with Ba outer-most. The calculated densities of states for the tilted geometry show distinct peaks above E(F) originating from Ba and W d-orbitals and are in good agreement with the experimental results.

Lamouri, A.↗